To achieve better cooling effect, general electric devices have at least one and/or above additional cooling fans installed inside whereon, so as to keep circulating air inside and outside the working environment of electric devices and exhale hot air from inside without causing instability of the systems due to high temperature.
General cooling fans in the past that utilized fixed rotating speeds, provided stable ventilation but sometimes failed to quickly and instantly exhale high heat resulting from heavy loaded operation of a computer system. Besides, some other cooling fans were designed to rotate with high speeds in order to heighten ventilation and achieve better cooling effect; nevertheless, such fans relatively incurred noise. Therefore, it is difficult for a user to use a fan with fixed high speed function to have better cooling results and also accept the noise interruption.
Recently some patent applicants develop fans with adjustable fan speed function. Such a fan enable a user to adjust quickly fan speed for exhaling heat from the inside of a electric device without additional extensive wirings to be connected to fan speed controlling parts; even when the fan speed needs to be slowed down the user can also adjust the fan to reduce noise.
However, the kind of fan with adjustable speed function needs an extended line to connect with other external electric parts, which are installed at other positions, so as to increase the complicity of the fan installation.